Filtering device and method for filtering a fluid

Abstract

The invention relates to a filtering device for filtering a fluid, in particular a liquefied plastic, comprising: a housing comprising a receptacle for receiving a screen carrier, a fluid inlet channel and a fluid outlet channel, and the screen carrier is received within the receptacle so as to be movable along a longitudinal axis within the housing, wherein the screen carrier has a screen carrier inlet, a screen carrier outlet and a cavity for receiving a screen plate with a filter element, wherein the cavity is connected in a fluid- conducting manner to the screen carrier inlet and the screen carrier outlet, and wherein the screen carrier can be moved from a screen change position via a venting position region into a filtering position. According to the invention, the housing has, adjacent to the fluid inlet channel, an inlet throttle recess which extends into the housing and is connected in a fluid-conducting manner to the fluid inlet channel and which, depending on the position of the screen carrier inlet relative to the inlet throttle recess in the venting position region, opens up a variable flow cross-section between the screen carrier inlet and the fluid inlet channel.

Description

[0001] Nordson Corporation; Case 24-021 / PCT

[0002] Filtering device and method for filtering a fluid

[0003]

[0001] The invention relates to a filtering device for filtering a fluid, in particular a liquefied plastic, comprising a housing comprising a receptacle for receiving a screen carrier, a fluid inlet channel and a fluid outlet channel, the screen carrier is received within the receptacle so as to be movable along a longitudinal axis withing the housing, wherein the screen carrier has a screen carrier inlet, a screen carrier outlet and a cavity for receiving a screen plate with a filter element, wherein the cavity is connected in a fluid-conducting manner to the screen carrier inlet and the screen carrier outlet, and wherein the screen carrier can be moved from a screen change position via a venting position region into a filtering position. Preferably, the longitudinal axis herein refers to a longitudinal axis of the screen carrier. Preferably the venting position region herein refers to a region of different positions in which the screen carrier can be moved such that air can escape from the cavity. Fluid-conducting manners herein may refer to the property that fluid but also air and other movable substances can be conducted.

[0004]

[0002] Filtering devices of the type mentioned at the outset are used, for example, in plastic-processing machines when high demands are placed on the purity of the plastic to be processed. They are typically arranged between an extrusion device, which melts and conveys the plastic, and an application device. Such filtering devices for filtering a fluid, in particular a liquefied plastic, and methods in question are known from the prior art. DE 10 2007 057 816 Al for example describes such a filtering device with a screen carrier in which a filter element is arranged on a screen plate.

[0005]

[0003] After some time in operation, a filter element has to be exchanged or cleaned. For the purpose of exchanging a filter element, the screen carrier is moved from a filtering position, also referred to as a production position, into a so-called screen change position in which access to the screen plate becomes possible and the filter element can be exchanged.

[0006]

[0004] After the filter element has been changed, it has to be brought back into the production process. In this case, the challenge arises that the interior spaces of the screen carrier, which are referred to as the cavity, are filled with air after the screen change and it is essential to prevent air from entering the plastic fluid flow. For this reason, after the screen change, the screen carrier is first moved into a venting position region in which liquefied plastic flows into the screen cavity and displaces the air contained therein to the outside via venting channels. After the cavity has been completely filled or vented, the liquefied plastic has to be set in motion again in order to start the filtering process. In this case, the effect is that the plastic melt exhibits a certain degree of inertia, which can cause undesired overall system pressure fluctuations during the process of accelerating the melt. It has therefore proved to be challenging to carry out the acceleration of the melt after it has come to a standstill such that the overall system pressure remains within narrowly definable limits.

[0007]

[0005] In order to overcome this problem, it is known from the prior art, e.g. EP 3424 679 Al, to arrange a filling recess adjacent to the screen carrier outlet, so that a flow cross section between the fluid outlet channel and the cavity can be adjusted with particular precision. In this way, in particular after the cavity has been completely vented, a connection of the cavity to the fluid outlet channel can be established via the throttle recess such that a gentle acceleration of the melt, in particular out of the cavity in the direction of the fluid outlet channel, is established. In other words, in this way, the melt received in the fluid inlet channel and in the empty cavity can be controlled such that the overall system pressure is virtually not influenced by the venting process or is at any rate kept within tolerable limit values.

[0008]

[0006] However, a disadvantage in this case is that, in particular during a screen change process in which the screen carrier and thus also the throttle recess are guided out of the heated housing, the screen carrier and thus also the throttle recess cool down rapidly. This causes the melt to harden in the groove when the groove cools down. This can lead to a blockage of the throttle groove, so that, after the screen carrier has been reintroduced into the housing, the throttle effect of the throttle recess can only be available to a limited extent. In the prior art, it is therefore common practice to remove the hardened melt located in the throttle recess manually, for example by means of a spatula. Furthermore, it has occasionally been observed that the throttle recess can be susceptible to soiling in the screen change position. Furthermore, errors or omissions can occur during the cleaning of the throttle recess.

[0009]

[0007] Another disadvantage in the prior art for the first purpose occurs on the device outlet side. After venting is completed, the cavity is filled entirely with melt flow and for re-entering into the filtration position, the screen carrier moves the cavity outlet to establish the needed fluid-connection with the respective melt fluid outlet. However, as soon as there is fluid connection between cavity and outlet, which will occur as soon as there is a very small overlap between the respective cross sections, the melt will flow with maximum velocity as there is no throttle effect. This causes major pressure fluctuation.

[0010]

[0008] For the second purpose of cleaning the filter element, the screen carrier is moved from the filtering position into a so-called backflushing position which is different from the screen change position. In this backflushing position, the filter element is backflushed with plastic melt flow that flows in a counter direction (opposite direction) to the filtering direction for the purpose of backflushing the filter and removing particles from the dirt side of the filter element (=cleaning). In this case, the plastic melt flow used for the backflushing is removed from the already filtered plastic melt. In the backflushing, there is usually no air that needs to be removed during a venting procedure. However, moving the screen carrier into the backflushing position or from the backflushing position back to the filtration position too quickly will have a negative effect on the system pressure.

[0011]

[0009] On top of that, for the backflushing of a filter element, the melt flow direction through this particular filter element changes which means that the melt flow velocity changes (reverses) and is zero at a certain point of time. Also, this change of velocity (acceleration as well as deceleration) of the melt flow should not cause pressure fluctuations, but - as a tradeoff - the time duration at which the melt flow has zero velocity should be at a minimum to avoid any solidification or at least avoid a significant increase of viscosity of the melt flow within the filter element.

[0012]

[0010] Such pressure fluctuations can lead to negative influences on the subsequent plastic production which can lead to product quality suffering. For instance, when spinning nozzles are used in a spin process, the spun threads can even tear off due to such pressure fluctuations

[0013] [OH] The object of the invention is to develop a device of the type mentioned at the outset to the effect that the disadvantages found in the prior art are eliminated as far as possible and further to address the problems that arise with the second purpose (cleaning / backflushing the filter element). The object of the invention was in particular to specify a filtering device in which, during a screen change process or backflushing (cleaning) of a filter element, the overall system pressure is kept as constant as possible and, at the same time, melt is prevented from hardening in an undesired manner, in particular during the screen change process or the backflushing process as well as melt received in the respective fluid inlet channel and in a filter cavity - empty or during backflushing with melt direction change - can be set in motion in slow manner such that the overall system pressure is virtually not influenced by the venting backflushing process or is at any rate kept within tolerable limit values and no solidification of melt occurs.

[0014]

[0012] According to the invention, the object is achieved in a filtering device of the type mentioned above in that the housing has, adjacent to the fluid inlet channel, an inlet throttle recess which extends into the housing and is connected in a fluid-conducting manner to the fluid inlet channel and which, depending on the position of the screen carrier inlet relative to the inlet throttle recess in the venting position region, releases a variable flow cross-section between the screen carrier inlet and the fluid inlet channel.

[0015]

[0013] The invention makes use of the knowledge that the arrangement of the inlet throttle recess in the housing ensures that the throttle recess always remains free of blockages by hardening melt. This is attributable to the fact that the housing itself is permanently heated using a heating element, such as an oil- or water- or electricitybased heating. So, the housing has (or remains) a temperature which is above the solidification temperature of the melt, for example at 270° C. to 285° C. for the plastic polyester (PET). If the throttle recess is arranged in the screen carrier, it has been observed that melt in the throttle recess hardens rapidly, already at 255° C., that is to say with only small temperature drops relative to the housing temperature. As a result of the fact that the inlet throttle recess is arranged according to the invention in the heated housing, such temperature drops and thus solidifications of the melt can be reliably prevented.

[0016]

[0014] At the same time, the inlet throttle recess achieves the effect that a free flow cross section between the fluid inlet channel and the cavity can be adjusted with particular precision. In this way, in particular after the cavity has been completely vented via the throttle recess, it can be achieved that a gentle acceleration of the melt takes place such that the cavity is filled with the melt via the inlet throttle recess and such that the overall system pressure is virtually not influenced by the acceleration process or is at any rate kept within tolerable limit values.

[0017]

[0015] According to one embodiment, the inlet throttle recess extends along the longitudinal axis, starting from the fluid inlet channel and as viewed in the venting position region, in the direction of the screen carrier inlet. In this way, it is ensured that the cavity is first connected to the fluid inlet channel via the inlet throttle recess, which allows particularly sensitive flooding of the cavity. According to one embodiment, in the venting position region the cavity is connected in a fluid-conducting manner exclusively to the fluid inlet channel.

[0018]

[0016] According to a second aspect of the invention, the housing has a throttle recess which is arranged adjacent to the screen carrier outlet and extends into the housing and which, depending on a position of the screen carrier outlet relative to the throttle recess, releases a variable flow cross-section between the screen carrier outlet and the fluid outlet channel.

[0017] According to a preferred embodiment, the housing has a throttle recess which is arranged adjacent to the screen carrier outlet and extends into the housing and which, depending on a position of the screen carrier outlet relative to the throttle recess, releases a variable flow cross-section between the screen carrier outlet and the fluid outlet channel.

[0019]

[0018] The second aspect of the invention and the previous preferred embodiment make use of the knowledge that the arrangement of the throttle recess adjacent to the screen carrier outlet allows a free flow cross-section between the fluid outlet channel and the cavity to be adjusted with particular precision. In this way, in particular after the cavity has been completely vented (the cavity is not empty anymore), a connection of the cavity to the fluid outlet channel can be established via the throttle recess such that a gentle acceleration of the melt, in particular out of the cavity in the direction of the fluid outlet channel, is established. This throttle recess has the effect of accelerating the melt in a slow and controlled manner after the cavity is already filled and the fluid-connection to the outlet should be established for returning into the filtration position. This change of velocity (acceleration as well as deceleration) of the melt flow is now controlled by this throttle recess and so, no pressure fluctuations occur. This also resolves the above mentioned tradeoff between time required to avoid pressure fluctuations and solidification of the melt due to no movement. So, the throttle recess avoids unwanted pressure fluctuations and unwanted solidification of the melt within the cavity when moving the carrier during backflushing or venting.

[0020]

[0019] As a further result of the fact that the throttle recess is arranged again in the heated housing, it is achieved, independently of the operating position, that the throttle recess is always heated such that solidification of melt is effectively prevented. As a result, manual removal of hardened melt can be prevented and, furthermore, high availability of the throttle recess can be ensured.

[0021]

[0020] According to a preferred development, the screen carrier can be moved from the venting position region via an acceleration position region into the filtering position, wherein the throttle recess, depending on a position of the throttle recess relative to the screen carrier outlet in the acceleration position region, releases a variable flow crosssection between the screen carrier outlet and the fluid outlet channel.

[0022]

[0021] The acceleration position region is preferably separated from the venting position region, wherein the acceleration of the melt thus takes place, in particular, only after passing through the venting position region, that is to say after the cavity has been completely vented.

[0022] According to one embodiment, the filtering device has a control device which is set up and designed such that it moves the screen carrier further via the acceleration position region in the direction of the filtering position by means of at least one control signal after the venting of the cavity such that the fluid outlet channel is initially connected in a fluid-conducting manner exclusively to the cavity by means of the throttle recess, and the screen carrier is moved in the direction of the filtering position such that a fluid pressure in the fluid inlet channel and / or in the fluid outlet channel remains within a definable pressure range.

[0023]

[0023] In this way, the throttle recess is used to achieve particularly advantageous control of the filter device. For example, it is also possible to define a specific maximum pressure drop which essentially predetermines the feed rate of the screen bolt. If, for example, an excessive pressure drop is observed, the feed speed of the screen carrier can be reduced. Otherwise, the feed speed of the screen carrier can also be increased if only a very small pressure drop which is lower than a defined limit value has been observed.

[0024]

[0024] According to one embodiment, the throttle recess extends along the longitudinal axis, starting from the fluid outlet channel as viewed in the venting position region, in the direction of the screen carrier outlet. Further, the throttle recess preferably has a cross section which varies in the direction of the longitudinal axis. As a result, sensitive adjustment of the free flow cross-section is possible.

[0025]

[0025] According to one embodiment, the cross section of the throttle recess extends, starting from the screen carrier outlet, in the direction of the longitudinal axis. The extension preferably takes place linearly, wherein the cross section has, in particular, a wedge-shaped or notch-shaped basic shape.

[0026]

[0026] According to a further aspect of the invention, the housing has a backflushing feed channel which is configured to feed backflushing fluid, starting from a clean side of the screen plate with the filter element, to the screen support plate with the filter element in a backflushing position region, and a backflushing channel which is configured to discharge backflushed fluid after the backflushing, wherein the screen carrier can be moved into a backflushing position region in which the backflushing feed channel is at least partially connected in a fluid-conducting manner to the clean side of the screen plate with the filter element, and the backflushing channel is at least partially connected in a fluid-conducting manner to the dirt side of the screen plate with the filter element, wherein the housing has, in the region of the receptacle, a backflushing recess which is arranged adjacent to the backflushing feed channel, is connected in a fluidconducting manner to the backflushing feed channel and extends into the housing, wherein the backflushing recess, depending on a position of the screen carrier outlet relative to the backflushing recess in the backflushing position region, releases a variable flow cross-section between the backflushing feed channel and the screen carrier outlet.

[0027]

[0027] According to a preferred embodiment, the housing has a backflushing feed channel which is configured to feed backflushing fluid, starting from a clean side of the screen plate with the filter element, to the screen plate with the filter element in a backflushing position region, and a backflushing channel which is configured to discharge backflushed fluid after the backflushing, wherein the screen carrier can be moved into a backflushing position region in which the backflushing feed channel is at least partially connected in a fluid-conducting manner to the clean side of the screen plate with the filter element, and the backflushing channel is at least partially connected in a fluid-conducting manner to the dirt side of the screen plate with the filter element, wherein the housing has, in the region of the receptacle, a backflushing recess which is arranged adjacent to the backflushing feed channel, is connected in a fluid-conducting manner to the backflushing feed channel and extends into the housing, wherein the backflushing recess, depending on a position of the screen carrier outlet relative to the backflushing recess in the backflushing position region, releases a variable flow crosssection between the backflushing feed channel and the screen carrier outlet.

[0028]

[0028] As a result of the fact that the backflushing recess is arranged in the housing, it is again achieved that the backflushing recess always participates in the heating of the housing and has a temperature which effectively prevents blockage of the backflushing recess on account of hardening melt. Moreover, the further aspect of the invention makes use of the knowledge that, in the backflushing position, a connection of the cavity to the backflushing channel is open with a large volume. The backflushing quantity is set via the backflushing recess between the backflushing feed channel and the cavity and therefore in the region of the clean side of the screen plate with the filter element. This takes place, in particular, in such a way that pressure fluctuations in the system are minimized. Relatively large dirt particles have no effect on the backflushing behavior. In contrast, in the prior art, the throttling, that is to say the overlap of cavity and backflushing channel, is often set on the dirt side. This can lead to blockages. In addition, for backflushing of the filter element, the melt flow direction through this particular filter element changes which means that the melt flow velocity changes (reverses) and is zero at a certain point of time. This change of velocity (acceleration as well as deceleration) of the melt flow is now controlled by this backflushing recess and so, no pressure fluctuations occur. This also resolves the above-mentioned tradeoff between time required to avoid pressure fluctuations and solidification of the melt due to no movement. So, the throttle recess avoids unwanted pressure fluctuations and unwanted solidification of the melt within the cavity when moving the carrier during backflushing or venting.

[0029]

[0029] According to one embodiment, the backflushing recess extends along the longitudinal axis, starting from the backflushing feed channel in the backflushing position region, in the direction of the screen carrier outlet.

[0030]

[0030] According to one embodiment, the backflushing recess has a cross section which varies in the direction of the longitudinal axis. This configuration ensures that the quantity of the fed melt can be adjusted with fine metering by varying the flow cross section between the backflushing feed channel and the cavity. According to one embodiment, the cross section of the backflushing recess tapers, in particular linearly, starting from the backflushing feed channel in the direction of the longitudinal axis. In this way, the melt used for the backflushing can be fed in very precisely and it can be ensured that the overall system pressure remains within definable limits. According to one embodiment, the cross section has a wedge-shaped or notch-shaped basic shape. These basic shapes contribute to the precise dosing of the melt used for the backflushing.

[0031]

[0031] According to a preferred embodiment, the filtering device has a control device which is set up and designed such that during the backflushing of the screen carrier it changes the position of the screen carrier by means of at least one control signal such that during the backflushing the fluid pressure in the fluid inlet channel and / or in the fluid outlet channel remains within a definable pressure range such that, during a movement of the screen carrier in the backflushing position region, a variable flow cross-section between the backflushing feed channel and the screen carrier outlet is opened up by means of the backflushing recess.

[0032]

[0032] According to a further aspect of the invention a method for filtering a fluid, in particular a liquified plastic, by means of a filtering device according to an aspect of the invention is disclosed. The method comprises moving the screen carrier in the receptacle of the housing along the longitudinal axis from the screen change position into the venting position region in which the inlet throttle recess, depending on the position of the screen carrier inlet relative to the inlet throttle recess, releases a variable flow crosssection between the screen carrier inlet and the fluid inlet channel. Further, the method comprises moving the screen carrier in the receptacle of the housing along the longitudinal axis from the venting position region into the filtering position.

[0033]

[0033] According to a preferred embodiment, the method accords to an parts of the aspect of the invention comprises moving the screen carrier in the receptacle of the housing along the longitudinal axis from the venting position region into the acceleration position region in which the throttle recess, depending on the position of the screen carrier outlet relative to the throttle recess, releases the variable flow crosssection between the screen carrier outlet and the fluid outlet channel. Further, the method comprises moving the screen carrier in the receptacle of the housing along the longitudinal axis from the acceleration position region into the filtering position.

[0034]

[0034] According to a further aspect of the invention a computer-readable storage medium on which a computer program is stored which, when executed on a computer, performs the method for filtering a fluid, in particular a liquified plastic, according to an aspect of the invention.

[0035]

[0035] Moreover, all aspects of the invention make use of the same advantages and preferred embodiments as the other aspects of the invention and vice versa.

[0036]

[0036] Further features and advantages of the invention result from the attached claims and the following description, in which exemplary embodiments are explained in detail with reference to schematic drawings.

[0037]

[0037] In the figures:

[0038] FIG. 1 first exemplary embodiment of a filtering device according to the invention in a sectional view in a venting position region;

[0039] FIG. 2 shows the exemplary embodiment of the filtering device according to the invention according to FIG. 1 in a detailed view;

[0040] FIG. 3 shows an alternative exemplary embodiment of a filtering device according to the invention in a backflushing position region in a sectional view.

[0041] FIG. 4 shows a flow diagram of a method according to the invention.

[0042]

[0038] FIG. 1 shows a filtering device 2 for filtering a fluid, in particular a liquefied plastic. The filtering device comprises a housing 4 with a receptacle 6 for receiving a screen carrier 8. The housing 4 furthermore comprises a fluid inlet channel 10 and a fluid outlet channel 12. The screen carrier 8 which is received so as to be movable along a longitudinal axis 26 is arranged within the receptacle 6. The screen carrier 8 has a screen carrier inlet 16, a screen carrier outlet 18 and a cavity 20 for receiving a screen plate with a filter element 22. The cavity 20 is connected in a fluid-conducting manner to the screen carrier inlet 16 and the screen carrier outlet 18. In this case, the screen carrier 8 can be moved from a screen change position (not shown in the figures) via a venting position region E, which is shown in FIG. 1, into a filtering position.

[0043]

[0039] The housing 4 has, adjacent to the fluid inlet channel 10, an inlet throttle recess 34 which extends into the housing 4. The inlet throttle recess 34 is connected in a fluidconducting manner to the fluid inlet channel 10. Depending on the position of the screen carrier inlet 16 relative to the inlet throttle recess 34 in the venting position region E, the inlet throttle recess 34 releases a variable flow cross-section 38 between the screen carrier inlet 16 and the fluid inlet channel 10.

[0044]

[0040] The inlet throttle recess 34 extends along the longitudinal axis 26, starting from the fluid inlet channel 10 and as viewed in the venting position region E, in the direction of the screen carrier inlet 16. In this case, in the venting position region E the cavity 20 is connected exclusively to the fluid inlet channel 10.

[0045]

[0041] The housing 4 furthermore has a throttle recess 24 which is arranged adjacent to the screen carrier outlet 18 and extends into the housing 4. Depending on a position of the screen carrier outlet 18 relative to the throttle recess 24, the throttle recess 24 releases a variable flow cross-section 30 between the screen carrier outlet 18 and the fluid outlet channel 12.

[0046]

[0042] The screen carrier 8 can furthermore be moved from the venting position region E via an acceleration position region into a filtering position which is not shown in any more detail. In this case, depending on a position of the throttle recess 24 relative to the screen carrier outlet 18 in the acceleration position region, the throttle recess 24 releases a variable flow cross-section 30 between the screen carrier outlet 18 and the fluid outlet channel 12.

[0047]

[0043] Furthermore, the filtering device has a control device 52 which is indicated in FIG. 1. The control device 52 is set up and designed such that it moves the screen carrier 8 further via the acceleration position region in the direction of the filtering position by means of at least one control signal after the venting of the cavity 20 such that the fluid outlet channel 12 is initially connected in a fluid-conducting manner exclusively to the cavity 20 by means of the throttle recess 24, and the screen carrier 8 can be moved in the direction of the filtering position such that a fluid pressure in the fluid inlet channel 10 and / or in the fluid outlet channel 12 remains within a defined or definable pressure range.

[0048]

[0044] In an embodiment, the screen carrier 8 moves along the throttle recess 24 step by step with some pauses or continuously at a slow speed without processing any control signals or, at a minimum, with only the feedback of the position of the screen carrier 8. This would allow the melt to accelerate smoothly.

[0049]

[0045] In another embodiment, pressure sensors may be installed that continuously measure the pressure at the outlet of the screen changer 8 and thus determine the desired pressure constancy when passing through the throttle recess 24 step by step.

[0050]

[0046] The throttle recess 24 extends along the longitudinal axis 26, starting from the fluid outlet channel and as viewed in the venting position region E, in the direction of the screen carrier outlet 18. In this case, the throttle recess 24 has a cross section 28 which varies in the direction of the longitudinal axis 26. In particular, the cross section 28 of the throttle recess 24 extends linearly, starting from the screen carrier outlet 18, in the direction of the longitudinal axis 26, wherein the cross section 28 has a wedge-shaped basic shape 32.

[0051]

[0047] The screen carrier 8 furthermore has a first venting recess 44, a second venting recess 42 and a third venting recess 40. Depending on the position of the venting recesses 40, 42, 44 relative to the housing 4, the venting recesses 40, 42, 44 connect the cavity 20 in a fluid-conducting manner to the surroundings. The venting recesses 40, 42, 44 extend along the longitudinal axis 26. The venting recesses 40, 42, 44 are configured as a groove and have a different longitudinal extent along the longitudinal axis 26. In the venting position region shown in FIG. 1, the air contained in the cavity 20 can flow out of the cavity via the venting recess 40, 42, 44. In this case, the first venting recess 44 is connected in a fluid-conducting manner to a first partial region of the cavity 50, the second venting recess 42 is connected in a fluid-conducting manner to a second partial region of the cavity 48and the third venting recess 40 is connected in a fluid-conducting manner to a third partial region of the cavity 46.

[0052]

[0048] FIG. 2 shows a detailed view of a section of the receptacle 6 of the housing 4, in which section the inlet throttle recess 34 is configured. As a result of the fact that the inlet throttle recess 34 is arranged in the housing 4 in the same way as the throttle recess 24 of FIG. 1, it can be ensured that said throttle recesses 24, 34 are always heated via the housing 4 and therefore hardening melt is prevented from settling in the region of the throttle recesses 24, 34 and blocking said throttle recesses.

[0053]

[0049] FIG. 3 shows a filtering device 102. The filtering device 102 has a housing 104 with a receptacle 106 for receiving a screen carrier 108. The housing 104 furthermore has a fluid inlet channel 110 and a fluid outlet channel 112. The screen carrier 108 is received within the receptacle 106 so as to be movable along a longitudinal axis 126. The screen carrier 108 has a screen carrier inlet 116, a screen carrier outlet 118 and a cavity 120 for receiving a screen plate with a filter element 122. The cavity 120 is connected in a fluidconducting manner to the screen carrier inlet 116 and the screen carrier outlet 118.

[0054]

[0050] The housing 104 has a backflushing feed channel 154 which is configured to feed backflushing fluid, starting from a clean side of the screen plate with the filter element 156, to the screen plate with the filter element 122 in a backflushing position region R, which is shown in FIG. 3. The housing 104 has a backflushing channel 160. The backflushing channel 160 is configured to discharge backflushed fluid after the backflushing. In the backflushing position region R, the backflushing feed channel 154 is at least partially connected in a fluid-conducting manner to a clean side 156 of the screen plate with the filter element 122. The backflushing channel 160 is at least partially connected in a fluid-conducting manner to the dirt side of the screen plate with the filter element 158. Preferably, the backflushed fluid herein refers to the backflushing fluid which has been backflushed through the screen plate with the filter element.

[0055]

[0051] The housing 104 has, in the region of the receptacle 106, a backflushing recess 162. The backflushing recess 162 is arranged adjacent to the backflushing feed channel 154, is connected thereto in a fluid-conducting manner and extends into the housing 104. Depending on a position of the screen carrier outlet 118 relative to the backflushing recess 162 in the backflushing position region R, the backflushing recess 162 releases a variable flow cross-section 164 between the backflushing feed channel 154 and the screen carrier outlet 118. In this case, the backflushing recess 162 extends along the longitudinal axis 126, starting from the backflushing feed channel 154 in the backflushing position region R, in the direction of the screen carrier outlet 118.

[0056]

[0052] The backflushing recess 162 has a cross section 166 which varies in the direction of the longitudinal axis 126. The cross section 166 of the backflushing recess 162 tapers linearly, starting from the backflushing feed channel 154, in the direction of the longitudinal axis 126. In this case, the cross section 166 has a wedge-shaped or notchshaped basic shape 132. The filtering device 102 shown in FIG. 3 also has a control device 152. The control device 152 is set up and designed such that during the backflushing of the screen carrier 108 it changes the position of the screen carrier 108 by means of at least one control signal such that during the backflushing the fluid pressure in the fluid inlet channel 110 and / or in the fluid outlet channel 112 remains within a definable pressure range such that, during a movement of the screen carrier 108 in the backflushing position region R, the variable flow cross-section 164 between the backflushing feed channel 154 and the screen carrier outlet 118 is released by means of the backflushing recess 162.

[0053] As a result of the fact that the backflushing recess 162 is also arranged in the housing 104, it is ensured that said backflushing recess 162 is always heated as part of the housing 104, so that melt is prevented from hardening in the region of the backflushing recess 162 and blocking said backflushing recess.

[0054] FIG. 4 shows a flow chart of a method M for filtering a fluid, in particular a liquified plastic, by means of a filtering device according to an aspect of the invention shown in FIG. 1 to 3. The method M comprises moving Ml the screen carrier 8, 108 in the receptacle 6, 106 of the housing 4, 104 along the longitudinal axis 26 from the screen change position into the venting position region E in which the inlet throttle recess 34, depending on the position of the screen carrier inlet 16, 116 relative to the inlet throttle recess 34, releases a variable flow cross-section 38 between the screen carrier inlet 16, 116 and the fluid inlet channel 10, 110. Further, the method M comprises moving M2 the screen carrier 8, 108 in the receptacle 6, 106 of the housing 4, 104 along the longitudinal axis 26 from the venting position region E into the filtering position.

[0057] Reference Signs List

[0058] 2 / 102 Filtering device 4 / 104 Housing 6 / 106 Receptacle 8 / 108 Screen carrier 10 / 110 Fluid inlet channel 12 / 112 Fluid outlet channel 16 / 116 Screen carrier inlet 18 / 118 Screen carrier outlet

[0059] 20 / 120 Cavity 22 / 122 Screen plate with filter element 24 Throttle recess 26 / 126 longitudinal axis 30 variable flow cross-section between the screen carrier outlet and the fluid outlet channel

[0060] 34 Inlet throttle recess 38 variable flow cross-section between the screen carrier inlet and the fluid inlet channel

[0061] 40 Third venting recess 42 Second venting recess

[0062] 44 First venting recess

[0063] 46 Third partial region of the cavity

[0064] 48 Second partial region of the cavity 50 First partial region of the cavity 52 / 152 Control device 154 Backflushing feed channel / fluid outlet channel 156 Clean side of the screen plate with filter element 158 Dirt side of the screen plate with filter element 160 Backflushing channel 162 Backflushing recess 164 variable flow cross-section between the backflushing feed channel and the screen carrier outlet

[0065] 166 cross section of the backflushing recess E Venting position region R Backflushing position region

Claims

Patent Claims1. Filtering device (2, 102) for filtering a fluid, in particular a liquefied plastic, comprising:- a housing (4, 104) comprising:- a receptacle (6, 106) for receiving a screen carrier (8, 108),- a fluid inlet channel (10, 110);- a fluid outlet channel (12, 120), and- the screen carrier (8, 108) is received within the receptacle (6, 106) so as to be movable along a longitudinal axis (26) within the housing (4), wherein the screen carrier (8, 108) has a screen carrier inlet (16, 116), a screen carrier outlet (18, 118) and a cavity (20, 120) for receiving a screen plate with a filter element (22, 122), wherein the cavity (20, 120) is connected in a fluid-conducting manner to the screen carrier inlet (16, 116) and the screen carrier outlet (18, 118), and wherein the screen carrier (8, 108) can be moved from a screen change position via a venting position region (E) into a filtering position, characterized in that the housing (4, 104) has, adjacent to the fluid inlet channel (10, 110), an inlet throttle recess (34) which extends into the housing (4, 104) and is connected in a fluid-conducting manner to the fluid inlet channel (10, 110), and which, depending on the position of the screen carrier inlet (16, 116) relative to the inlet throttle recess (34) in the venting position region (E), releases a variable flow cross-section (38) between the screen carrier inlet (16, 116) and the fluid inlet channel (10, 110).

2. Filtering device (2, 102) according to claim 1, wherein the inlet throttle recess (34) extends along the longitudinal axis (26), starting from the fluid inlet channel (10, 110) and as viewed in the venting position region (E), in the direction of the screen carrier inlet (16, 116).

3. Filtering device (2, 102) according to one of the preceding claims, wherein in the venting position region (E) the cavity (20, 120) is connected in a fluidconducting manner exclusively to the fluid inlet channel (10, 110).

4. Filtering device (2, 102) according to the preamble of claim 1, wherein the housing (4, 104) has a throttle recess (24) which is arranged adjacent to the screen carrier outlet (18, 118) and extends into the housing (4, 104),and which, depending on a position of the screen carrier outlet (18, 118) relative to the throttle recess (24), releases a variable flow cross-section (30) between the screen carrier outlet (18, 118) and the fluid outlet channel (12, 120).

5. Filtering device (2, 102) according to one of the claims 1 to 3, wherein the housing (4, 104) has a throttle recess (24) which is arranged adjacent to the screen carrier outlet (18, 118) and extends into the housing (4, 104), and which, depending on a position of the screen carrier outlet (18, 118) relative to the throttle recess (24), releases a variable flow cross-section (30) between the screen carrier outlet (18, 118) and the fluid outlet channel (12, 120).

6. Filtering device (2, 102) according to one of the preceding claims 4 to 5, wherein the screen carrier (8, 108) can be moved from the venting position region (E) via an acceleration position region into the filtering position, and wherein the throttle recess (24), depending on a position of the throttle recess (24) relative to the screen carrier outlet (18, 118) in the acceleration position region, releases the variable flow cross-section (30) between the screen carrier outlet (18, 118) and the fluid outlet channel (12, 120).

7. Filtering device (2, 102) according to claim 6, characterized by a control device (52) which is set up and designed such that it moves the screen carrier (8, 108) further via the acceleration position region in the direction of the filtering position by means of at least one control signal after the venting of the cavity (20, 120) such that the fluid outlet channel (12, 120) is initially connected in a fluid-conducting manner exclusively to the cavity (20, 120) by means of the throttle recess (24), and the screen carrier (8, 108) is moved in the direction of the filtering position such that a fluid pressure in the fluid inlet channel (10, 110) and / or in the fluid outlet channel (12, 120) remains within a definable pressure range.

8. Filtering device (2, 102) according to one of the claims 4 to 7, wherein the throttle recess (24) extends along the longitudinal axis (26), starting from the fluid outlet channel (12, 120) and as viewed in the venting position region (E), in the direction of the screen carrier outlet (18, 118).

9. Filtering device (2, 102) according to one of the claims 4 to 8, wherein the throttle recess (24) has a cross section (28) which varies in the direction of the longitudinal axis (26).

10. Filtering device (2, 102) according to claim 9, characterized in that the cross section (28) of the throttle recess (24) extends, starting from the screen carrier outlet (18, 118), in the direction of the longitudinal axis (26).

11. Filtering device (2, 102) according to claim 10, characterized in that the cross section (28) of the throttle recess (24) extends linearly, starting from the screen carrier outlet (18, 118), in the direction of the longitudinal axis (26), wherein the cross section (28) has, in particular, a wedge-shaped or notch-shaped basic shape (32).

12. Filtering device (2, 102) according to the preamble of claim 1, wherein the housing (104) has a backflushing feed channel (154) which is configured to feed backflushing fluid, starting from a clean side (156) of the screen plate with the filter element (22, 122), to the screen plate with the filter element (22, 122) in a backflushing position region (R), and a backflushing channel (160) which is configured to discharge backflushed fluid after the backflushing, wherein the screen carrier (8, 108) can be moved into a backflushing position region (R) in which the backflushing feed channel (154) is at least partially connected in a fluid-conducting manner to the clean side (156) of the screen plate with the filter element (22, 122), and the backflushing channel (160) is at least partially connected in a fluid-conducting manner to the dirt side (158) of the screen plate with the filter element (22, 122), wherein the housing (104) has, in the region of the receptacle (6, 106), a backflushing recess (162) which is arranged adjacent to the backflushing feed channel (154), is connected in a fluid-conducting manner to the backflushing feed channel (154) and extends into the housing (104), wherein the backflushing recess (162), depending on a position of the screen carrier outlet (18, 118) relative to the backflushing recess (162) in the backflushing position region (R), releases a variable flow cross-section (164) between the backflushing feed channel (154) and the screen carrier outlet (18, 118).

13. Filtering device (2, 102) according to one of the claims 1 to 12, wherein the housing (104) has a backflushing feed channel (154) which is configured to feed backflushing fluid, starting from a clean side (156) of the screen plate with thefilter element (22, 122), to the screen plate with the filter element (22, 122) in a backflushing position region (R), and a backflushing channel (160) which is configured to discharge backflushed fluid after the backflushing, wherein the screen carrier (8, 108) can be moved into a backflushing position region (R) in which the backflushing feed channel (154) is at least partially connected in a fluid-conducting manner to the clean side (156) of the screen plate with the filter element (22, 122), and the backflushing channel (160) is at least partially connected in a fluid-conducting manner to the dirt side (158) of the screen plate with the filter element (22, 122), wherein the housing (104) has, in the region of the receptacle (6, 106), a backflushing recess (162) which is arranged adjacent to the backflushing feed channel (154), is connected in a fluid-conducting manner to the backflushing feed channel (154) and extends into the housing (104), wherein the backflushing recess (162), depending on a position of the screen carrier outlet (18, 118) relative to the backflushing recess (162) in the backflushing position region (R), releases a variable flow cross-section (164) between the backflushing feed channel (154) and the screen carrier outlet (18, 118).

14. Filtering device (2, 102) according to claim 12 or 13, wherein the backflushing recess (162) extends along the longitudinal axis (126), starting from the backflushing feed channel (154) in the backflushing position region (R), in the direction of the screen carrier outlet (18, 118).

15. Filtering device (2, 102) according to one of the claims 12 to 14, wherein the backflushing recess (162) has a cross section (166) which varies in the direction of the longitudinal axis (126).

16. Filtering device (2, 102) according to one of the claims 12 to 15, characterized in that the cross section (166) of the backflushing recess (162) tapers, in particular tapers linearly, starting from the backflushing feed channel (154) in the direction of the longitudinal axis (126).

17. Filtering device (2, 102) according to one of the claims 12 to 16, characterized in that the cross section (166) has a wedge-shaped or notch-shaped basic shape (132).

18. Filtering device (2, 102) according to one of the claims 12 to 17, characterized by a control device (152) which is set up and designed such that during the backflushing of the screen carrier (8, 108) it changes the position of the screen carrier (8, 108) by means of at least one control signal such that during the backflushing the fluid pressure in the fluid inlet channel (10, 110) and / or in the fluid outlet channel (12, 112) remains within a definable pressure range such that, during a movement of the screen carrier (8, 108) in the backflushing position region (R), the variable flow cross-section (164) between the backflushing feed channel (154) and the screen carrier outlet (18, 118)is opened up by means of the backflushing recess (162).

19. Method (M) for filtering a fluid, in particular a liquified plastic, by means of a filtering device according to one of the claims 1 to 18, wherein the method (M) comprises the following steps:- moving (Ml) the screen carrier (8, 108) in the receptacle (6, 106) of the housing (4, 104) along the longitudinal axis (26) from the screen change position into the venting position region (E) in which the inlet throttle recess (34), depending on the position of the screen carrier inlet (16, 116) relative to the inlet throttle recess (34), releases a variable flow cross-section (38) between the screen carrier inlet (16, 116) and the fluid inlet channel (10, 110);- moving (M2) the screen carrier (8, 108) in the receptacle (6, 106) of the housing (4, 104) along the longitudinal axis (26) from the venting position region (E) into the filtering position.

20. Method (M) for filtering a fluid, in particular a liquified plastic, by means of the filtering device according to one of the claims 4, 6 to 11, wherein the method (M) comprises the following steps:- moving the screen carrier (8, 108) in the receptacle (6, 106) of the housing (4, 104) along the longitudinal axis (26) from the venting position region (E) into the acceleration position region in which the throttle recess (24), depending on the position of the screen carrier outlet (18, 118) relative to the throttle recess (24), releases the variable flow cross-section (30) between the screen carrier outlet (18, 118) and the fluid outlet channel (12, 112);- moving the screen carrier (8, 108) in the receptacle (6, 106) of the housing (4, 104) along the longitudinal axis (26) from the acceleration position region into the filtering position.

21. Method (M) for filtering a fluid, in particular a liquified plastic, by means of a filtering device according to one of the claims 1 to 18, wherein the method (M) comprises the following steps:- moving the screen carrier (8, 108) in the receptacle (6, 106) of the housing (4, 104) along the longitudinal axis (26) into the backflushing position region (R) in which the backflushing feed channel (154) is at least partially connected in a fluid-conducting manner to the clean side (156) of the screen plate with the filter element (22, 122), and the backflushing channel (160) is at least partially connected in a fluid-conducting manner to the dirt side (158) of the screen plate with the filter element (22, 122).

22. Computer-readable storage medium on which a computer program is stored which, when executed on a computer, performs the method for filtering a fluid, in particular a liquified plastic, according to one of the claims 19 to 21.

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